1. Field of the Invention
This invention, relates to a process for preparing an attrition resistant vanadium-antimony oxide catalyst by adding to a vanadium-antimony oxide catalyst slurry a lithium compound which upon contact with the aqueous catalyst slurry provides hydroxide ions, such as lithium hydroxide or lithium carbonate. More particularly, this invention relates to a process for preparing an attrition resistant vanadium-antimony oxide catalyst involving preparing a catalyst slurry containing vanadium oxide and antimony oxide and other elements, adding lithium in the hydroxide form to the catalyst slurry, concentrating the catalyst slurry to increase the solids content of the catalyst slurry, and drying the catalyst slurry to form attrition resistant particles of vanadium-antimony catalyst.
The attrition resistant vanadium-antimony oxide catalyst of the present invention may be used in any oxidation or ammoxidation reactor. Catalysts made according to this invention are preferably used in fluid bed or transport line reactors, requiring hard, microspheroidal catalysts. These fluid bed or transport line reactors include variants with catalyst fluidized or conveyed by fast vapor streams, such as spouted beds. Ammoxidation reactors where part of the oxygen is supplied to the catalyst in an external regenerator are also well adapted to the use of such vanadium-antimony oxide catalysts.
The catalyst of the present invention is useful for the oxidation and ammoxidation of paraffins, olefins, and alkylaromatic compounds in a reaction zone. In particular, the ammoxidation of propane or propylene with ammonia and oxygen to make acrylonitrile, the ammoxidation of methylpyridine with ammonia and oxygen to make the corresponding cyanopyridine, the ammoxidation of m-xylene with ammonia and oxygen to make isophthalonitrile and the oxidation of o-xylene to make phthalic anhydride.
2. Description of the Prior Art
U.S. Pat. No. 4,879,264, discloses a process for making vanadium and antimony oxide catalysts which can contain lithium. Further, U.S. Pat. 5,008,427, discloses a process for preparing vanadium-antimony oxide catalysts for propane and isobutane ammoxidation in which lithium can be added to the catalyst as lithium nitrate. Neither patent discloses a process for preparing a vanadium-antimony oxide catalyst by adding a lithium compound which upon contact with the aqueous catalyst slurry provides hydroxide to the catalyst slurry. In particular, neither of these patents discloses adding lithium hydroxide or lithium carbonate to the catalyst slurry. These patents do not suggest that the attrition resistance of vanadium-antimony oxide catalysts is improved by adding at least part of lithium in a form which provides hydroxide ions to the catalyst slurry. It has been discovered that these vanadium-antimony oxide catalysts which do provide lithium at least in part by adding the lithium in a form which provides hydroxide ions upon contact with the catalyst slurry have high attrition resistance.
It is desirable to have a process for preparing vanadium-antimony oxide catalysts which have improved attrition resistance.